Interlock mechanism for prevention of simultaneous operation of two switch devices



M. Y. TURNBULL 3,303,300 ISM FOR PREVENTION OF SIMULTANEOUS OPERATION OF TWO SWITCH DEVICES Feb. 7, I967 INTERLOCK MECHAN 2 Sheets-Sheet 1 Filed July 20, 1965 INVENTOR.

MERL/N Y. TURNBULL Feb. 7, 1967 M Filed July 20; 1965 Y. TURNBULL 3,303,300

INTERLOCK MECHANISM FOR PREVENTION OF SIMULTANEOUS OPERATION OF TWO SWITCH DEVICES 2 Sheets-Sheet z INVENTOR.

MERLIN )4 TURNBULL United States Patent INTERLOCK MECHANISM FOR PREVENTHQN 0F This nivention relates to interlock mechanisms and is particularly concerned with a mechanism which will provide a mounting base for a pair of devices and prevent simultaneous operation of the devices.

While the interlock disclosed herein may be used to prevent simultaneous operation of a variety of devices other than electromagnetically operated switches, it is particularly suited for use with the type illustrated in application Serial No. 473,299 concurrently filed herewith on July 20, 1965 and which has been assigned by the inventors Joseph J. Gribble, Kenneth J. Merien, and Harold E. Whiting to the assignee of the present invention. The electromagnetically actuated switch, as disclosed in the Gribble et a1. application, is provided with a base which positions a plurality of pairs of stationary contacts and a carrier which supports a plurality of movable contacts which are arranged to bridge the pairs of stationary contacts when the carrier is moved along an axis perpendicular to the base. An electromagnet motor carried above the base causes the carrier to move from i an inoperative position, wherein the movable contacts are separated from the stationary contacts, to an operative position wherein the bridging engagement between the stationary and movable contacts occurs. The base is provided with an opening axially aligned with the axis of the carrier to expose a portion of the carrier to a bottom mounting surface for the base.

In its preferred form, the interlock mechanism according to the present invention provides both a support for mounting a pair of devices in spaced relation to a mounting panel and a mechanism which is positioned between the devices and the mounting panel which will prevent simultaneous movement of movable members of both switches along an axis perpendicular to the panel to an operative position. Also, the interlock will require that both switches be nearly in the contact opening position before either of the switches can begin to move to the contact closing position and will preclude bridging or jamming of the mechanism even if both switches so be energized for simultaneous movement to the contact closing position.

It is, therefore, an object of this invention to provide an improved mechanical interlock especially adapted for interlocking two companion switches with a mechanism which may be readily applied without change to a pair of switches when the switches are mounted either side by side or in tandem one above the other on the interlock.

Another object is to provide an interlock which may be applied, with a minimum modification in length of a pair of links, to a pair of switches which may be mounted either side by side or in tandem at various distances from each other on a mounting panel.

A still further object is to provide an interlock which while especially adapted for use with two electromagnetically actuated switches is equally useful for preventing simultaneous movement in one direction of any two movable members.

An additional object is to provide an interlock mechanism which will prevent the simultaneous operation of a pair of independently operable electric switches which are supported by the mechanism on a mounting panel so the bases of the switches are spaced from the panel and to provide a means for preventing the simultaneous operation of the switches in the space between the switches and the panel so the interlock mechanism will not interfere with free access to the wire connecting terminals of the switches or the components of the switches which require inspection and service.

Further objects and features of the invention will be readily apparent to those skilled in the art from the specification and appended drawings illustrating certain preferred embodiments in which:

FIG. 1 is a side elevational view of a pair of switching units mounted side by side on a mechanical interlock structure according to the present invention with portions of the interlock structure and one of the switches broken away to illustrate constructional details of the mechanical interlock structure and the connection between the plungers of the interlock mechanism and a movable member of the switches.

FIG. 2 shows, as detached in a bottom plan view, the operating mechanism for the interlock mechanism in FIG. 1 so the portions thereof may be more readily identified.

FIG. 3 is an exploded view showing in perspective certain components of the mechanical interlock mechanism in FIG. 2.

FIG. 4 is an end view of the interlock mechanism in FIG. 1 with the switching units removed.

In FIG. 1 of the drawings, a pair of switches, indicated by numerals A and 20B, are shown as mounted on a mechanical interlock assembly 10. The switches 20A and 20B are of the type disclosed in the Gribble et a1. application and include a base 12 of insulating material which positions a plurality of pairs of spaced stationary contacts, not shown. Positioned above and carried by the base 12 is a housing 14 which encloses a magnet motor which moves a member 16 from a position shown by the switch 20B downwardly along an axis perpendicular toward the base 12 to an operated position illustrated by the switch 20A, when magnet is energized to operate the switch 20A. The member 16 carries a plurality of movable contacts, not shown, which are arranged to engage the stationary contacts on the base 12 to complete an electric circuit therebetween when the member 16 is positioned as shown by the switch 20A and to be moved out of engagement with the stationary contacts so as to interrupt the circuit through the stationary contacts when the member 16 is positioned as shown by the switch 20B, The member 16 has a ledge 18 formed thereon which presents a bottom surface 22 which is aligned along the axis of movement of the member 16 with an opening 24 in the bottom wall of the base 12. Thus the surface 22 is exposed through the opening 24 through the bottom wall of the base 16. The switches 20 are also provided with suitable metal mounting plates 26 to which are secured the bases 12. The plates 16 are provided with openings which are aligned with the openings 24 to expose the surface 22 to the bottom of the switch assemblies which include the mounting plates 26.

The pair of switch assemblies 20A and 20B each have their respective mounting plates 26 secured to a support 30 of the mechanical interlock assembly 10. The support 30 is formed as a U-shaped channel member having a web portion 31 equal in width to the plates 26 and a pair of spaced arms 32 downwardly extending from the web portion 31. The web portion 31 is sized to permit the mounting of the switches 20A and 2013 in a side by side position on a top surface 33 of the web portion 31 and is provided with openings 34 which are aligned with the openings 24 in the bases 12 and similarly located openings in the mounting plates 26 so the bottom surfaces 22 of the ledges 18 of the switches 20A and 20B are exposed to a bottom surface 35 of the web 31. The

spaced arms 32, which are formed to extend along the marginal edges of theweb portion 31, are provided with suitable openings to receive screws 36, for attaching the entire assembly, including the switch assemblies A and 208, as well as the support xto a panel 37. The arms 32 are formed to extend downwardly sufficiently to provide space between the bottom surfaces of the switches 20A and 20B wherein the operating mechanism 38 of the mechanical interlock assembly 10 which is carried by the bottom surface 35 is received.

The operating mechanism 38 includes a pair of mechanisms, 39 and 40 which are interconnected by a pair of lever bars 41. As each of the mechanisms 39 and 40 are identical and are arranged to face on opposite directions on the bottom surface 35, only the mechanism 39 will be specifically described. The mechanism 39 includes a channel member 42 which has a web portion 43 and a pair of spaced arms 44 which extend in a plane which extends through-the spaced arms 44 of the actuator 40 and which plane is perpendicular to the bottom surface 35. The web portion 43 is provided with an opening 45 centered between the arms 44 and aligned with the opening 34 when the web portion 43 is secured to the bottom surface 35. Each of the arms 44 is provided with a notch 46. The notch 46 is shaped to have a semicircular portion 47 having a radial center located in a plane which is perpendicular to a common centerline which passes through the centers of the openings 24, 34 and 45. The notches 46 further are shaped to provide a horizontal edge 48 which extends '-tangentially of the portion of the semicircular portion 47 adjacent the web 43 and a curved surface 49' which extends tangentially of the portion of the semicircular portion 47 remote from the web 43. The curved surface 49 has a relatively small radius compared to the radius of the semicircular portion 47 and extends to an edge 50 Which is slightly inclined toward the horizontal edge 48. Secured to the web 43 on opposite sides of the opening 45 along a centerline passing through the openings 45 of the mechanisms 39 and 40 are a pair of guide members 51, each of which extend perpendicular to the web 43 and parallel to the spaced arms 32. h p

Asmost clearly shown in FIGS. 1 and 3, the mechanism 39 also includes a plunger 52, a pair of levers 53, a pair of pivot pins 54 and 55 and a pair of return springs 56 and 57. The plunger 52 is provided with a stem portion 58 which extends upwardly in alignment with the vertical axis of movement of the member 16 to an upper free end 59 which is positioned to engage the bottom surfaceZZ of the ledge 18. Formed on the lower end of the stem portion 58 is a base portion 60 which has a bore 61. The bore 61 extendsthrough the base portion 60 perpendicular to the axis of the stem portion 58 and provides a bearing journal for the pivot pin 54. Spaced on the base'portion 60 on, opposite sides of the bore 61 are guide portions '62 and 63 which project downwardly from the base portion 60 and each have bores 64 and 65 which are slidable on the guide members 51.

The guide members 51 are located on the web 43 so the guide portion 62 and the bore 64 are spaced at a greater distance from the stem 58 than the guide portions 63 and the bore 65. A round bottom surface 66 is formed on the base portion 60. The surface 66 is .delined by a portion of a cylindrical surface having its radial center located at the axial center of the bore 61. The portion of the surface 66 adjacent the guide portions 62 is provided with a clearance notch 67. The base portion 60 is also provided with straight flat surfaces 68 and 69 which lie in planes parallel to a plane extending through the axis of the bores 64 and 65.

The levers 53 each have a bore 70 on one end which is received by an end of the pivot pin 54 and is maintained assembled on the ends of the pivot pin 54 by retainers 71 which may be received in suitable grooves at the ends of the pivot pin 54. When the levers 53 are thus assembled on the pivot pin 54, the fiat surfaces 68 and 69 will guide the levers 53 in a straight line path of pivotal movement. The other end of each of the levers 53 is provided with a bore 72 which receives the pivot pin 55. The bores 70 and 72 are spaced on the levers 53 so the pivot pin 55 will roll on the curved bottom sur face 66 when the levers rotate about the pivot pin 54.

The return springs 56 and 57, which are positioned between spring seats 73 and 74 on the free end of the guide members 51 and the portion 60, normally urge the plunger 52 upwardly to a position wherein the base portion 60 engages the web 43. The guide portions 62 and 63, which are received within the convolutions of the springs 56 and 5'7, guide the springs during compression.

The lever bars 41 each have an opening at its opposite end which is received by an end of the pivot pin 55 which projects beyond the outer surface of the levers 53. The lever bars 41, levers 53 and the pivot pin 55 are maintained assembled by retainers 75 which are received in suitable grooves 76 formed on the free ends of the pivot pins 55. The openings in each lever bar 41 which receive the pivot pins 55 are spaced from each other so that when the levers 41 and 53 are assembled, the levers 53 will be inclined from a vertical centerline passing through axis of the stem 58 of the plunger 52. The incline of the levers 53 is arranged so that the pivot pins 55 are spaced a lesser distance from each other than the space between the pivot pins 54 of the mechanisms 39 and 40.

Each of the lever bars 41 has guide portions 77 thereon. The guide portions 77 are formed as projections which extend beyond the notches 46 and are arranged to slidingly engage the inner surfaces of the spaced arms 44. Additionally positioned between the retainers 75 and the outer surfaces of the lever bars 41 by the pivot pins 55 are rollers 78. The rollers 78 have a slightly smaller diameter than the semicircular portions 47 and are-arranged to engage and roll upon the horizontal edge 48 when the assembly of the foregoing parts is completed.

In view of the foregoing description, the operation and advantages of the mechanical interlock assembly is as follows.

When switch assemblies 28A and 20B are both dcenergized, the return springs 56and 5'7 urge both plungers 52 upwardly thereby maintaining an engagement between the free end 59 and the ledge 18. Also the levers 53 will be inclined at substantially equal angles toward each other, thereby positioning the rollers '78 of the mechanisms 39 and 40 equidistantly from the bottoms of the semicircular portions 47. When the rollers 78 are thus positioned, a vertical line of centers through the axis of the pivot pins 55 will lie forwardly of the inclined edge 50 while a portion of the rollers 78 will be vertically aligned with the curved surfaces 49' When either of the switch assemblies 20A or 20B is energized, eg, the s'witch'assembly 20B in FIG. 1, the member 16 is moved vertically downwardly. The ver= tical downward movement of the member 16 of the switch assembly 2613 moves the plunger 52 of the actuator 40 downwardly against the forces exerted by the springs 56 and 57. p

The initial downward movement of the plunger 52 causes the pivot levers 53 of the mechanism 46* to move clockwise to a more inclined position while the pivot lever 53 of the mechanism 39 moves clockwise toward a more vertical position relative to a center line passing through the axis of the stem 58. The clockwise movement of the levers 53 of the mechanisms 39 and 40 is accompanied by a horizontal movement to the left of the lever bars 41 to a limiting position wherein the rollers 78 seatwithin the semicircular portion 47 of the mechanism 39. 7 When the lever bars 41 are thus positioned, the rollers 78 of the mechanism 40 will be external of the semicircular portions 47 of the mechanism 40. During the foregoing movements, the rollers 78 will roll upon the horizontal edges 48 and the pivot pin 55 will roll on the rounded bottom surface 66.

A continued downward movement of the plunger-52 of the mechanism 40, after the rollers 78 of the mechanism 39 are seated in the semicircular portion 47, causes the rollers 78 of the mechanism 40 to move in a generally vertical path as the lever bars 41 pivot about the pivot provided by the seated rollers 78 in the semicircular portions 47 of the mechanism 39. When the switch 20B is fully energized, the ledge 18 will be at its lowest downward position and the rollers 78 of the mechanism 40 will be moved to their final interlocking position wherein they are horizontally aligned with the inclined edge 50 of the mechanism 40.

During the movement of the rollers 78 to their final position, the guide portions 77 will guide the movement of the lever bars 41 and the curved surfaces 49 will prevent any interference to movements of the rollers 78 to the interlocking position.

If the switch 20A should be energized while the rollers 78 of the mechanism 40 are in an interlocking position, the downward movement of the plunger 52 of the mechanism 39 will be prevented because the lever bars 41 are prevented from movements to the right by an engagement of the rollers '78 with the inclined edge 50 of the mechanism 40. This arrangement will maintain the seating engagement of the rollers 78 in the semicircular portions 47 of the mechanism 39 and prevent downward movement of the plunger 52 of the mechanism 39 to thereby prevent movement of the member 16 of the switch assembly 20A to its energized position.

In view of the foregoing description it is obvious that energization of the switch assembly 20A will prevent movement of the member 16 of the switch assembly 203 to an energized position should the switch assembly 20B be energized subsequent to the energization of the switch assembly 20A.

In the event both switch assemblies 20A and 20B are simultaneously energized, the members 16 or both of the switch assemblies 20A and 26B will be prevented from moving to their energized position as follows. When the switches 20A and 28B are simultaneously energized, the plungers 52 of both of the mechanisms 39 and 40 will move downwardly an insignificant distance to a position wherein the rollers 78 of the mechanisms 39 and 40 move into engagement with the curved surfaces 49 and thereby prevent a continued downward movement of the plungers 52 of the mechanisms 39 and 40. When the switch assemblies 20A and 20B are simultaneously de-energized, the interlock assembly, including the rollers 78 of mechanisms 39 and 40, will return to their at-rest position previously described. Alternately, if one of the switch assemblies is de-energized, and the other switch assembly remains energized, e.g., switch assembly 20A is de-energized while the switch assembly 20B remains energized, the interlock mechanism, including the rollers 78 will move to the position previously described wherein the rollers 78 of the mechanism 39 are seated in the semicircular portions 47 while the rollers 78 of the mechanism 40 are positioned adjacent the inclined surface 50.

The movements to the proper positions of the interlock mechanism upon simultaneous energization of both of the switches 20A and 20B and then a subsequent deenergization of one of the switches 20A or 20B is accomplished without frictional interference between any of the moving parts of the entire interlock mechanism which would normally prevent such movements.

It is to be noted that when both switch assemblies 20A and 28B are simultaneously energized, the parts of the interlock assembly are essentially moved to a jammed condition. Frequently, in other types of mechanicalinterlocks, when this condition is encountered, a subsequent de-energization of either one or both of the switch assemblies 20A and/or 203 will not restore the operative condition of the interlock mechanism. Rather, the interlock 6 mechanism can be returned to an operative condition only if tools are used to force the interlock mechanism from its jammed state.

In contrast, the interlock mechanism according to the present invention will not only relieve itself of its jammed condition but will instantly move to its proper interlocking position.

As previously stated, the levers 53 of the mechanism 39 and are positioned by the lever bars 41 so the levers 53 of the mechanisms 39 and 40 are inclined toward each other. Thus when both of the switches 20A and 20B are simultaneously energized, the levers 53 of both of the mechanisms 39 and 48 will move vertically downwardly without rotational movement about the pivot pins 54 and 55 to a position wherein the rollers 78 of the mechanisms 39 and 40 engage the curved surfaces 49. When the rollers 78 are thus positioned, a circumferential portion of the roller 78 of the mechanism 39 to the left of a vertical centerline through the pivot pin 55 will engage the curved surface 49 of the mechanism 39 while a circumferential portion of the roller 78 of the mechanism 40 to the right of a vertical centerline through the pivot pin 55 will engage the curved surface 49 of the mechanism 40. Thus any further movements of the rollers 78 of both of the mechanisms 39 and 40 is prevented as the rollers 78 and inclined levers 53 of the mechanisms 39 and 40 constantly apply forces in opposite directions.

When one of the switch assemblies 20A or 20B is deenergized while the other switch assembly, e.-g., switch assembly 2GB remains energized, the interlock mechanism will move without assistance to prevent re-energization of. the switch assembly 20A as long as the switch assembly 203 remains energized. When the switch assembly 20A is de-energized, the downward vertical force causing an engagement of the rollers 78 of the mechanism 39 with the curved surfaces 49 is removed, while the downward vertical force which causes the rollers 78 to engage the curved surface 49 of the mechanism 40 continues. The continued force on the mechanism 48 causes two phenomena to occur for moving the lever bars 41 to the proper interlocking position. The incline of lever 53 of the mechanism 40 to the left causes the levers 53 to move downwardly and to the left to an interlocking position with the inclined edge 58 as the rollers 78 of the mechanism 40 roll over the curved surface 49. Similarly, the curved surface 49 permits the rollers 78 of the mechanism 39 to rotate and move upwardly without frictional binding into a seating position in the semicircular portions 47 where the rollers 78 thus prevent switch assembly 20A from being energized.

In the foregoing description the switch assemblies 20A and 20B are indicated as energized and de-energized. These terms are used to indicate the operational movements of the members 16 and without consideration of the electrical condition of the magnet motors of the switch assemblies. Further it will be seen that as the interlocking mechanism 10 is positioned between the switching assemblies 20A and 20B and the panel 37, the switching assemblies are completely accessible from the front of the panel 37. This arrangement will permit the switching assemblies 20A and 20B to re readily wired and serviced without disturbing or interference from the interlock mechanism 10.

While certain preferred embodiments of the invention have been specifically disclosed, it is understood that the invention is not limited thereto, as many variations will be readily apparent to those skilled in the art and the invention is to be given its broadest possible interpretation within the terms of the following claims.

What is claimed is:

1. An interlock for preventing simultaneous operation of a pair of independently operable switches comprising: a channel-like mounting member having a pair of spaced openings in an upper surface of the member for mounting the pair of switches side by side in spaced relation to a mounting panel so an element of each of the switches which is movable along an :axis normal to the surface is aligned with one of the openings when the switch providing the element is energized, a pair of plungers each having a base portion and a stem portion, resilient means mounting each of said plungers so the base portions of each of said plungers is carried in a space between a bottom surface of the member and the panel and the stem portions of each of the plungers extends through one of the openings into engagement with the element of one of the switches, said resilient means being arranged so each of the plungers is bodily movable along the axisof movement of the element which it engages, a pair of arms each having an end pivotally mounted on the body por: tion of one of the plungers and a free end extending from the body portion, a roller rotatably mounted on a pivot carried on the free end of each of the arms, a link pivotally mounted on the pivots of the arms for interconnecting the arms and causing the arms to be inclined toward one another, and a pair of members each having a notch portion wherein one of the rollers is positioned, each of said notch portions having an edge extending generally parallel to the axis for limiting movement of the roller along an axis parallel to the surface in one direction when one of the switches is energized and a semicircular portion for receiving the roller and limiting movement of the roller in a direction opposite said one direction when the other of said switches is energized.

2. In an interlock of the character described, a channellike mounting member, a pair of spaced plunger assemblies carried by the mounting member, each of said assemblies including: a plunger having a base portion and a stem portion, resilient means mounting the plunger so the base portion is carried in a space between a bottom surface of the member and a mountingpanel and the stem portion extends through an opening in the bottom surface in the member, said resilient means being arranged so the plunger is bodily movable along an axis normal to the bottom surface, an arm pivotally mounted on the body portion to have a free end exending from the body portion, a roller mounted on the free end of the arm, and a member having a notch for receiving the roller when the plunger is in either of two positions, said notch having an edge extending generally parallel to the axis which is en-' gaged by the roller when the plunger is in one of its two positions and a semicircular portion which is engaged by the roller when the plunger is in the other of its two positions, and a link interconnecting the free ends of both plunger assemblies so the arms of both assemblies are inclined toward each other.

3. A mechanical interlock for preventing concurrent closure of two switches wherein each of said switches has an element axially movable from one position along a linear axis to a second position upon closure of the switch, comprising: a channel-like mounting member having a surface normal to the axis for mounting the two switches side by side in spaced relation to a mounting panel so each element is axially aligned with an opening in said surface, a pair of plungers each having a base portion and a stem portion, resilient means mounting each of said plungers so the base portions of each of said plungers is carried in a space between a bottom surface of the member and the panel and the stem portions of each of the plungers extends through one of the openings into engagement with the element of one of the switches, said resilient means being arranged so each of the plungers is bodily movable along the axis of movement of the element which it engages, a pair of parallel arms each having an end pivotally mounted on the body portion of one of the plungers and a free end extending from the body portion, a roller rotatably mounted on a pivot carried on the free end of each of the arms, a pair of parallel links each having an end pivotally mounted on the pivots of one of the arms for interconnecting the arms and causing the arms on the plungers to be inclined toward one another, and a pair of members each having a notch portion wherein one of the rollers is positioned, each of said notch portions having an edge extending generally parallel to'the axis for limiting movement of the roller along an axis parallel to the surface in one direction when one of the switches is energized and a semicircular portion for -re ceiving the roller and limiting movement of the roller in a direction opposite said one direction when the other of said switches is energized,

4. An interlock for preventing simultaneous actuation of a pair of switches comprising: a mounting member having a surface for mounting the switches in side by side relation in spaced relation to a mounting panel, a pair of plungers each resiliently carried by the member for movement from an at-rest position along an axis normal to the surface to an actuated position upon actuation of one of the switches, a pair of parallel arms pivoted on each of the plungers for rotation in parallel planes, a roller carried on each of the pair of arms, a pair of parallel links connecting the pairs of parallel arms on each of the pair of plungers, a pair of channel-like members each providing a pair of parallel and spaced walls mounted on the mounting member so the parallel walls, parallel links and parallel arms are in parallel planes, and a notch in each of the parallel walls having an edge extending generally parallel to the axis engageable by one of the rollers for limiting movement of a parallel link in one direction when one of the switches is actuated and a semicircular portion engageabie by the roller for limiting movement of. the link in a direction opposite said one direction when the other of said switches is energized.

5. A mechanical interlock for preventing the simultaneous operation of a pair of independently operable devices, each of said devices having a mounting base and a member movable along an axis perpendicular to the base when the device is operated, comprising: a mounting member securable to a mounting panel, said mounting member having a pair of spaced openings extending between a top and a bottom surface of the mounting member for supporting the devices side by side so the mounting bases are in spaced relation to the mounting panel and the openings are aligned with the axis of the movable members, a pair of mechanisms secured on the bottom surface of the mounting member between the panel and bottom surface, each of said pair of mechanisms having: a pair of arms extending in a pair of planes, which planes are perpendicular to the bottom surface and spaced on opposite sides of the opening, a movable plunger having a base portion movable between the arms and a stem axially extending along the axis from the base portion through one of the openings engaging an end of a movable member of one of the devices, resilient means engaging the base portion for guiding the plunger movement along the axis of movement of the member which it engages and for urging the base portion toward the bottom surface, a pair of movable levers each having an end rotatably mounted on the base portion between the arms of the mechanism and a free end extending from the base portion, a pivot on the free end of each of the lever-s, a pair of parallel links connecting the pivots on the free ends of the pair of levers on one of the said pair of mechanisms with the pivots on the free ends of the pair of levers of. the other of said pair of mechanisms causing the pair of levers of the said one and the said other pairs of mechanisms to be inclined toward one another when neither of the devices is operated, a notch in each of the arms of both of said pair of mechanism, and a roller carried by the pivot on each of the levers to be positioned in one of the notches, each of the notches having an edge extending parallel to the axis for limiting movement of the roller positioned therein along an axis parallel to the top surface in one direction when one of the devices is operated and a semicircular edge tor receiving the roller and limiting movement of the roller in a direction oppo- 9 site said one direction when the other of said pair of devices is operated.

6. The combination as recited in claim 5 wherein the resilient means includes a pair of guides extending through the base portion on opposite sides of the axis and spring positioned by the guides for constantly urging the stem axially into engagement with the movable member of the device.

7. The combination as recited in claim 5 wherein each link has a surface guided by one of the arms when one of the plungers is moved by the operation of one of the devices.

8. The combination as recited in claim 5 wherein the mounting member has mounting portions formed along the marginal edges extending from the bottom surface to provide the space between the mounting panel and bottom surface wherein the pair of mechanisms and the pair of links are received when the stem portions of the plunger project from the space through the openings to present an end of the stem which is engaged by an end of the movable member.

No references cited.

ROBERT K. SCHAEFFER, Primary Examiner. I. B. SCOTT, Assistant Examiner. 

1. AN INTERLOCK FOR PREVENTING SIMULTANEOUS OPERATION OF A PAIR OF INDEPENDENTLY OPERABLE SWITCHES COMPRISING: A CHANNEL-LIKE MOUNTING MEMBER HAVING A PAIR OF SPACED OPENINGS IN AN UPPER SURFACE OF THE MEMBER FOR MOUNTING THE PAIR OF SWITCHES SIDE BY SIDE IN SPACED RELATION TO A MOUNTING PANEL SO AN ELEMENT OF EACH OF THE SWITCHES WHICH IS MOVABLE ALONG AN AXIS NORMAL TO THE SURFACE IS ALIGNED WITH ONE OF THE OPENINGS WHEN THE SWITCH PROVIDING THE ELEMENT IS ENERGIZED, A PAIR OF PLUNGERS EACH HAVING A BASE PORTION AND A STEM PORTION, RESILIENT MEANS MOUNTING EACH OF SAID PLUNGERS SO THE BASE PORTIONS OF EACH OF SAID PLUNGERS IS CARRIED IN A SPACE BETWEEN A BOTTOM SURFACE OF THE MEMBER AND THE PANEL AND THE STEM PORTIONS OF EACH OF THE PLUNGERS EXTENDS THROUGH ONE OF THE OPENINGS INTO ENGAGEMENT WITH THE ELEMENT OF ONE OF THE SWITCHES, SAID RESILIENT MEANS BEING ARRANGED SO EACH OF THE PLUNGERS IS BODILY MOVABLE ALONG THE AXIS OF MOVEMENT OF ELEMENT WHICH IT ENGAGES, A PAIR OF ARMS EACH HAVING AN END PIVOTALLY MOUNTED ON THE BODY PORTION OF ONE OF THE PLUNGERS AND A FREE END EXTENDING FROM THE BODY PORTION, A ROLLER ROTATABLY MOUNTED ON A PIVOT CARRIED ON THE FREE END OF EACH OF THE ARMS, A LINK PIVOTALLY MOUNTED ON THE PIVOTS OF THE ARMS FOR INTERCONNECTING THE ARMS AND CAUSING THE ARMS TO BE INCLINED TOWARD ONE ANOTHER, AND A PAIR OF MEMBERS EACH HAVING A NOTCH PORTION WHEREIN ONE OF THE ROLLERS IS POSITIONED, EACH OF SAID NOTCH PORTIONS HAVING AN EDGE EXTENDING GENERALLY PARALLEL TO THE AXIS FOR LIMITING MOVEMENT OF THE ROLLER ALONG AN AXIS PARALLEL TO THE SURFACE IN ONE DIRECTION WHEN ONE OF THE SWITCHES IS ENERGIZED AND A SEMICIRCULAR PORTION FOR RECEIVING THE ROLLER AND LIMITING MOVEMENT OF THE ROLLER IN A DIRECTION OPPOSITE SAID ONE DIRECTION WHEN THE OTHER OF SAID SWITCHES IS ENERGIZED. 